Cariótipos e evolução cromossômica de lagartos da subfamília Teiinae (Teiidae) com contribuições sobre a partenogênese
Arquivos
Data
2022-09-23
Autores
Castello, Rodrigo Jardim [UNIFESP]
Orientadores
Pellegrino, Katia Cristina Machado [UNIFESP]
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
Os estudos citogenéticos em lagartos da subfamília Teiinae (Teiidae) ainda são restritos a menos de 50% das espécies conhecidas, sendo a maioria baseado em coloração convencional. Essa abordagem permite identificar variações cromossômicas espécie-específicas úteis à sistemática e taxonomia, principalmente de grupos complexos, bem como na compreensão sobre a evolução cromossômica e origem de espécies assexuadas. Estas espécies partenogenéticas são formadas principalmente por eventos de hibridização e, em Squamata, a maioria pertence à subfamília Teiinae. Este trabalho pretendeu ampliar a caracterização dos cariótipos de espécies sexuadas e partenogenéticas de Teiinae, assim como discutir a evolução cromossômica da subfamília e seus gêneros num contexto filogenético. Foram amostradas nove espécies e quatro novas linhagens de Ameivula, Cnemidophorus, Glaucomastix e Kentropyx em coloração convencional e diferencial (AgNO3 e Banda C) e para reconstruir o número de cromossomos e estrutura do cariótipo ancestral de Teiinae, foi empregado o software ChromEvol v.2.0 e a função rayDisc (pacote CorHMN) no software R. Dentre as linhagens sexuadas, Ameivula apresentou 2n=50 e NF=86, G. itabaianensis 2n=48/50 e NF=80, e Kentropyx 2n e NF=50; e a constrição secundária e AgRON foram observadas na região distal do braço longo de ambos os homólogos dos pares 5, 5 e 1, respectivamente. Nas linhagens assexuadas de provável origem híbrida A. aff. nativo apresentou 2n=49 (NF=78), A. nativo 2n=48 (NF=72) e C. cryptus 2n=50 (NF=51) todas com heteromorfismos em diferentes pares e a constrição secundária e AgRON ativa na região distal do braço longo de apenas um homólogo dos pares 4, 3 e 1, respectivamente. Marcações bandas C positivas foram observadas em regiões centroméricas e teloméricas de Ameivula e Kentropyx, não havendo cromossomos parcial ou totalmente heterocromáticos em G. itabaianensis. A reconstrução do número e estrutura inferiu que o cariótipo ancestral de Teiinae possuía 2n e NF=50 com RON no par 1 e de Ameivula e Glaucomastix 2n=50, NF=86 e RON no par 5. Os cariótipos descritos confirmam a amplitude cariotípica de Teiinae (2n=46 a 56), não sendo encontradas variações espécies-específicas na AgRON e Bandas C. O cariótipo conservado das espécies sexuadas de Ameivula na Caatinga pode ser decorrente de fluxo gênico frequente, com formação de híbridos não partenogenéticos. O cariótipo de G. itabaianensis é o segundo descrito para o gênero e sugerimos uma possível presença de cromossomos B, embora análises complementares sejam ainda necessárias. A dominância nucleolar foi constatada nas espécies partenogenéticas, as quais provavelmente devem estar expressando a cópia materna do DNAr. Adicionalmente, os heteromorfismos cromossômicos e a reconstrução da ploidia e estrutura do cariótipo ancestral de A. nativo e C. cryptus trazem contribuições que apoiam a hipótese de hibridização para a origem dessas partenoformas. Com base nas reconstruções, hipotetizamos que a evolução cromossômica de Teiinae ocorreu principalmente por meio de fissões cêntricas e inversões pericêntricas, onde o número de braços é o caráter mais variável entre os gêneros e alguns grupos de espécies em Teiinae. Futuras abordagens utilizando técnicas de citogenética molecular, poderão revelar evidência de variações espécie-específicas e permitir uma melhor compreensão sobre os rearranjos nos cariótipos das espécies sexuadas e partenogenéticas que moldaram a evolução cromossômica de Teiinae.
The cytogenetic studies in lizards of the Teiinae (Teiidae) subfamily are still restricted to less than 50% of the known species, with the majority based on conventionally stained karyotypes. This approach allows the identification of species-specific chromosomal variations useful in systematics and taxonomy, especially regarding complex groups, as well as to understand chromosomal evolution and the origin of unisexual species. These species arose usually by events of hybridization, and in Squamata, most of them belong to Teiinae subfamily. The present study aimed to characterize the karyotypes of sexual and parthenogenetic species of Teiinae and discuss the chromosomal evolution of the subfamily and its genera under a phylogenetic context. We karyotyped nine species and four new lineages of Ameivula, Cnemidophorus, Glaucomastix e Kentropyx under conventionally and differentially-staining (AgNO3 and C-banding), and to reconstruct the ploidy and the structure of the Teiinae ancestral karyotype, we used the software ChromEvol v.2.0 and the rayDisc function (CorHMN package) at software R. Among the sexual lineages, Ameivula showed a karyotype with 2n=50 and FN=86, G. itabaianensis 2n=48/50 and FN=80, and Kentropyx 2n and NF=50, and a secondary constriction at the distal end of pairs 5, 5 e 1, respectively, on which the AgNOR was located. Among the asexual lineages, A. aff. nativo exhibited 2n=49 (FN=78), A. nativo 2n=48 (FN=72) and C. cryptus 2n=50 (FN=51) all presenting heteromorphisms at different pairs, and a secondary constriction at the distal end of pairs 4, 3 and 1, respectively, which harbors the AgNOR. Positive C-bands were localized at centromeric and telomeric regions of chromosomes in Ameivula and Kentroyx, but either completely or partial heterochromatic chromosomes were not observed in the karyotype of G. itabaianensis. The ancestral reconstructions of ploidy and karyotype structure support an ancestral karyotype of 2n and FN=50 with NOR located at pair 1 for Teiinae, and 2n=50, FN=86 with NOR at pair 5 for Ameivula and Glaucomastix. The karyotypes description herein agrees with the Teiinae chromosomal range (2n=46 to 56), however specie-specific variation at AgNOR and C-banding were not found. The conserved karyotype of sexual species of Ameivula from Caatinga may be due to frequent gene flow, but without origin of parthenogenetic individuals. G. itabaianensis is the second species karyotyped so far and we suggest a possible occurrence of B chromosome, although complementary analyses are still required. We verified the occurrence of nucleolar dominance at the parthenogenetic species, with maternal rDNA copy being probably expressed and dominant over the male rDNA copy. Additionally, chromosomal heteromorphisms and the ancestral reconstruction of ploidy and karyotype structure bring contributions that support the hybrid origin of A. nativo and C. cryptus. Based on the reconstructions, we hypothesized that centric fissions and pericentric inversions rearrangements may be involved in chromosome evolution of Teiinae, where the arm number is the most variable character between the genera and some species groups of the subfamily. Molecular cytogenetic approaches should present new evidence about specie-specific variations and allow us to better understand the rearrangements that are involved in chromosome evolution of sexual and unisexual species of Teiinae.
The cytogenetic studies in lizards of the Teiinae (Teiidae) subfamily are still restricted to less than 50% of the known species, with the majority based on conventionally stained karyotypes. This approach allows the identification of species-specific chromosomal variations useful in systematics and taxonomy, especially regarding complex groups, as well as to understand chromosomal evolution and the origin of unisexual species. These species arose usually by events of hybridization, and in Squamata, most of them belong to Teiinae subfamily. The present study aimed to characterize the karyotypes of sexual and parthenogenetic species of Teiinae and discuss the chromosomal evolution of the subfamily and its genera under a phylogenetic context. We karyotyped nine species and four new lineages of Ameivula, Cnemidophorus, Glaucomastix e Kentropyx under conventionally and differentially-staining (AgNO3 and C-banding), and to reconstruct the ploidy and the structure of the Teiinae ancestral karyotype, we used the software ChromEvol v.2.0 and the rayDisc function (CorHMN package) at software R. Among the sexual lineages, Ameivula showed a karyotype with 2n=50 and FN=86, G. itabaianensis 2n=48/50 and FN=80, and Kentropyx 2n and NF=50, and a secondary constriction at the distal end of pairs 5, 5 e 1, respectively, on which the AgNOR was located. Among the asexual lineages, A. aff. nativo exhibited 2n=49 (FN=78), A. nativo 2n=48 (FN=72) and C. cryptus 2n=50 (FN=51) all presenting heteromorphisms at different pairs, and a secondary constriction at the distal end of pairs 4, 3 and 1, respectively, which harbors the AgNOR. Positive C-bands were localized at centromeric and telomeric regions of chromosomes in Ameivula and Kentroyx, but either completely or partial heterochromatic chromosomes were not observed in the karyotype of G. itabaianensis. The ancestral reconstructions of ploidy and karyotype structure support an ancestral karyotype of 2n and FN=50 with NOR located at pair 1 for Teiinae, and 2n=50, FN=86 with NOR at pair 5 for Ameivula and Glaucomastix. The karyotypes description herein agrees with the Teiinae chromosomal range (2n=46 to 56), however specie-specific variation at AgNOR and C-banding were not found. The conserved karyotype of sexual species of Ameivula from Caatinga may be due to frequent gene flow, but without origin of parthenogenetic individuals. G. itabaianensis is the second species karyotyped so far and we suggest a possible occurrence of B chromosome, although complementary analyses are still required. We verified the occurrence of nucleolar dominance at the parthenogenetic species, with maternal rDNA copy being probably expressed and dominant over the male rDNA copy. Additionally, chromosomal heteromorphisms and the ancestral reconstruction of ploidy and karyotype structure bring contributions that support the hybrid origin of A. nativo and C. cryptus. Based on the reconstructions, we hypothesized that centric fissions and pericentric inversions rearrangements may be involved in chromosome evolution of Teiinae, where the arm number is the most variable character between the genera and some species groups of the subfamily. Molecular cytogenetic approaches should present new evidence about specie-specific variations and allow us to better understand the rearrangements that are involved in chromosome evolution of sexual and unisexual species of Teiinae.